Grain size sensitive deformation mechanisms in naturally deformed peridotites

Warren, J. M.; Hirth, Greg

doi:10.1016/j.epsl.2006.06.006

Cited by 321 publications

(313 citation statements)

References 37 publications

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“…A temperature of 600 • C likely represents the lower base of the seismogenic zone for the oceanic lithosphere, as seismological studies found that the occurrence of earthquakes in the oceanic lithosphere appear to be limited in depth range by the 600 • C isotherm Ekström, 2001, 2003;McKenzie et al, 2005). Consistently, evidence from naturally and experimentally deformed peridotite was presented that the transition from brittle to plastic deformation occurs at about 600 • C (e.g., Jaroslow et al, 1996;Warren and Hirth, 2006;Boettcher et al, 2007;Druiventak et al, 2011). Depending on the pair of activation enthalpies used, significant transformation will occur after tens to hundreds of years or it may last up to ten thousands of years until volume fractions of detectable size have undergone this specific microstructural transformation.…”

Section: Extrapolation To Natural Conditionsmentioning

confidence: 49%

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Trepmann¹,

Renner

Druiventak

2013

Solid Earth

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Abstract. Experiments comprising sequences of deformation (at 300 or 600 • C) and annealing at varying temperature (700 to 1100 • C), time (up to 144 h) and stress (up to 1.5 GPa) were carried out in a Griggs-type apparatus on natural olivine-rich peridotite samples to simulate deformation and recrystallization processes in deep shear zones that reach mantle depth as continuations of seismically active faults. The resulting olivine microfabrics were analysed by polarization and electron microscopy (SEM/EBSD, TEM). Core-and-mantle-like microstructures are the predominant result of our experiments simulating rapid stress relaxation (without or with minor creep) after a high-stress deformation event: porphyroclasts (> 100 µm) are surrounded by new grains comprising fragments and recrystallized grains with a wide range in size (2 to 40 µm). Areas with small grains (≤ 10 µm) trace former high-strain zones generated during initial high-stress deformation even after annealing at a temperature of 1100 • C for 70 h. A weak crystallographic preferred orientation (CPO) of new olivine grains is related to the orientation of the original host crystals but appears unrelated to the strain field. Based on these findings, we propose that olivine microstructures in natural shear-zone peridotites with a large range in grain size, localized fine-grained zones, and a weak CPO not related to the strain field are diagnostic for a sequence of high-stress deformation followed by recrystallization at low stresses, as to be expected in areas of seismic activity. We extended the classic Avrami-kinetics equation by accounting for time-dependent growth kinetics and constrained the involved parameters relying on our results and previous studies devoted to the kinetics of defect processes in olivine. Extrapolation to natural conditions suggests that the observed characteristic microstructure may develop within as little as tens of years and less than ten thousands of years. These recrystallization microstructures have a great diagnostic potential for past seismic activity because they are expected to be stable over geological timescales, since driving forces for further modification are not sufficient to erase the characteristic heterogeneities.

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Section: Extrapolation To Natural Conditionsmentioning

confidence: 49%

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Trepmann¹,

Renner

Druiventak

2013

Solid Earth

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“…Furthermore, mylonites collected from the Shaka fracture zone on the South West Indian Ridge provide additional evidence for the location of the boundary between seismic and aseismic deformation. The microstructures preserved in the mylonites indicate that they formed during localized viscous deformation at temperatures in the range of 600-800°C [Warren and Hirth, 2006]. Thus our experiments, seismological observations, and microstructures from oceanic dredge samples all point to approximately 600°C as the bounding isotherm for seismic activity in the oceanic lithosphere.…”

Section: Discussionmentioning

confidence: 71%

Olivine friction at the base of oceanic seismogenic zones

2007

Self Cite

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[1] We investigate the strength and frictional behavior of olivine aggregates at temperatures and effective confining pressures similar to those at the base of the seismogenic zone on a typical ridge transform fault. Triaxial compression tests were conducted on dry olivine powder (grain size 60 mm) at effective confining pressures between 50 and 300 MPa (using Argon as a pore fluid), temperatures between 600°C and 1000°C, and axial displacement rates from 0.06 to 60 mm/s (axial strain rates from 3 Â 10 À6 to 3 Â 10 À3 s À1 ). Yielding shows a negative pressure dependence, consistent with predictions for shear enhanced compaction and with the observation that samples exhibit compaction during the initial stages of the experiments. A combination of mechanical data and microstructural observations demonstrate that deformation was accommodated by frictional processes. Sample strengths were pressure-dependent and nearly independent of temperature. Localized shear zones formed in initially homogeneous aggregates early in the experiments. The frictional response to changes in loading rate is well described by rate and state constitutive laws, with a transition from velocity-weakening to velocity-strengthening at 1000°C. Microstructural observations and physical models indicate that plastic yielding of asperities at high temperatures and low axial strain rates stabilizes frictional sliding. Extrapolation of our experimental data to geologic strain rates indicates that a transition from velocity weakening to velocity strengthening occurs at approximately 600°C, consistent with the focal depths of earthquakes in the oceanic lithosphere.

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“…A mechanism that has possibly contributed to deformation in the San Quintín xenoliths is dislocationaccommodated grain boundary sliding. This mechanism is increasingly recognized as an important deformation process in both plagioclase-rich rocks (Kruse and Stünitz, 1999;Kenkmann and Dresen, 2002;Svahnberg and Piazolo, 2010;Hansen et al, 2013;Miranda et al, 2016) and olivine-rich rocks (Hirth and Kohlstedt, 1995;Warren and Hirth, 2006;Drury et al, 2011;Hansen et al, 2011;Précigout and Hirth, 2014;Chatzaras et al, 2016). Although the large grain sizes in the San Quintín xenoliths imply that dislocation creep is the dominant deformation mechanism, transition to diffusion creep at grain sizes that are larger than expected is facilitated by the high homologous temperatures estimated in some of the mafic granulites.…”

Section: Deformation Mechanisms In the Baja California Lithospherementioning

confidence: 99%

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

et al. 2017

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Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.

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Grain size sensitive deformation mechanisms in naturally deformed peridotites

Cited by 321 publications

References 37 publications

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Olivine friction at the base of oceanic seismogenic zones

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

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